What if we could see sound?
Wouldn’t it be great if all those different tunes made shapes around people who listen to them? It would allow us to meet the acoustic phenomena a little bit more in person. The Chladni plate experiment gives that idea a push (0r a pulse, so to speak). With a little salt and a vibrating plate, you can actually see sounds!
A German scientist, Ernst Chladni, was the first to prove that sound propagates in waves.
The big revelation came in the late 1700s. Chladni experimented to see if the sound traveled via waves through its medium. The medium around us is the air, but the same goes for any liquid or solid form.
It’s interesting to explore Chladni’s background a little bit.
He wasn’t studying to be a scientist, instead, he obtained a law degree, because that’s what his father wanted. Sadly, Chladni’s dad passed away in 1782, shortly after Chladni finished with his studies. He only wanted to make his father proud, and nothing tied him to law after his father’s passing. Chladni returned to physics and proved that meteors come from outer space, and not from volcanoes. Then he proceeded to play in the acoustics field and created the famous Chladni plate experiment.
To do the experiment yourself, you’ll need a metal plate, some material to dust the plate and something to create a sound with.
Then take sand, salt or flour and spread a thin layer of it all across the plate—in this example, the experiment is conducted with sand.
The man who experimented also used a tone generator and a speaker.
He attached the plate to a speaker. Then the tone generator was used to generate different frequencies, beginning with 345Hz and going up to 6050Hz.
As the pitch of the tone increased, different complex geometric shapes appeared on the plate.
The beautiful sandy shapes that appear are all because of resonance!
According to Wikipedia, resonance “describes the phenomenon of increased amplitude that occurs when the frequency of a periodically applied force is equal or close to a natural frequency of the system on which it acts.” What exactly does it mean? In essence, it’s that everything around us vibrates at ist set of natural frequencies, just as the plate does in this experiment.
The tone that was generated is also a wave, and it has its own frequency.
Because the metal plate was fixed to a speaker, every tone that came out of the speaker directly affected the plate. The frequencies of the tones that were generated “came in contact” with the natural frequencies of the plate.
The resonance did the job of increasing the vibration in some areas of the plate, and other areas were left with no vibration at all.
Because of the increased vibration in some areas, the sand was forced to move and it stayed still where there was no vibration at all.
The outcome is the magnificent, incredible sand ornamentation!
Once people understood the experiment, they started using it a lot.
Violin makers use the Chladni experiment to test if the back and front plates of the violin’s resonance box are symmetrical.
The practice of visualizing sound can help in the process of designing a concert hall, people also use it to decide where to place certain furniture in a room, and even when analyzing fluid-filled pipes.
Who knew that such a simple experiment could be so helpful?! Well, more than 15 million people who’ve seen the YouTube video had the opportunity to learn something new. Science never fails to amaze us!
Check out the full experiment in the clip below:
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